OBJECTIVE--To determine whether enterovirus RNA can be demonstrated in archival necropsy material in acute myocarditis. DESIGN--Analysis of paraffin embedded myocardial tissue from cases of acute myocarditis. SETTING--University virology department. METHODS--Extraction of RNA from tissue followed by polymerase chain reaction (PCR) and DNA sequence analysis. PATIENTS--Six patients with histologically proven myocarditis and eight controls. RESULTS--Enterovirus RNA was identified in 5 of 6 patients with myocarditis and in none of the controls. The nucleotide sequences of the PCR products showed greatest similarity to group B coxsackieviruses, particularly coxsackievirus B3. CONCLUSION--This study indicates that archival tissue samples, even histologically stained tissue sections, can be used to study the role of enteroviruses in myocardial disease using molecular detection techniques. If a predominant role for coxsackievirus B3 in myocarditis is confirmed by further study, this may have implications for the development of a specific vaccine.